The present invention relates generally to the distribution of information on a wireless communications network and more particularly to the distribution of communication information on a MMDS network.
Video information is distributed over a communications network generally in two conventional ways (wireless (i.e., MMDS) and wireline (CATV)). Either of these services can be analog or digital.
A conventional wireless video signal is transmitted in a predetermined frequency range from a one-way broadcast video transmission site in a first polarization (i.e., either horizontal or vertical). The wireless video signal is then received at a customer site in the same polarization, via a video antenna.
To more particularly describe a conventional MMDS video distribution system, refer now to FIG. 1.
FIG. 1 is a block diagram of a conventional video distribution system 100 which, for example, operates over a range of up to 35 miles. A video signal is transmitted from a broadcast video transmission site 106 by an antenna 102 in a given polarization such as horizontal polarization. In this system, the antenna 102 is designed such that cross-polarization rejection is typically at some minimum value such as 20 dB. Accordingly, the effective radiated power of this transmitter may be up to hundreds of Watts. The video signal is then received in the same (horizontal) polarization by a video antenna 108 at a customer site 104.
One conventional frequency range that video signals are transmitted in such a system is between 2150-2162 Mhz and 2500-2686 MHz (i.e., 33 6 MHz channels). This frequency spectrum is referred to as a multichannel multipoint distribution system (MMDS).
Background information regarding local multipoint distribution systems (LMDS) (28 GHz) with details of cellular techniques, polarization diversity, spatial diversity, and frequency reuse can be found in U.S. Pat. No. 4,747,160, issued May 24, 1988 to Bossard. Background information regarding point-to-multipoint radio communication system including a master station and a plurality of remote stations which communicate with the master station using frequency division multiplexing can be found in U.S. Pat. No. 4,528,656, issued Jul. 9, 1985 to Morais. Other patents that discuss polarized modulation or the use of horizontal and vertical polarization in the context of radio transmissions include U.S. Pat. No. 2,992,427, issued Jul. 11, 1961 to Franco; U.S. Pat. No 3,882,393, issued May 6, 1975 to Epstein; U.S. Pat. No 4,220,923, issued Sep. 2, 1980 to Pelchat et al.; U.S. Pat. No 4,321,705, issued Mar. 23, 1982 to Namiki; and U.S. Pat. No 4,521,878, issued Jun. 4, 1985 to Toyonaga. Finally, U.S. Pat. No. 3,864,633, issued Feb. 4, 1975 to Stenglein, and U.S. Pat. No 4,525,861, issued Jun. 25, 1985 to Freeburg may be of general relevance.
In analog MMDS systems, as before mentioned, the response channels from the customer site have been limited (typically by FCC regulation) to a small bandwidth (125 kHz wide) for voice or data transmission. The bandwidth of these response channels severely limits their use to transmit information from the customer site to the transmission site. The use of the frequencies are restricted typically by the communication authorities.
Accordingly, what is needed is a system and method for allowing more information to be distributed over a digital MMDS network. The system and method should be easily implemented, cost effective and easily adaptable to existing communication networks. The present invention addresses such a need.
The present invention comprises a MMDS broadcast digital video cell system on one polarization and a smaller array of cells, designed for two way services that use the orthogonal polarization in the same area.
The present invention includes a method for distributing information in a MMDS network comprising the steps of providing a video signal in a first polarization and a first direction to a first area, the video signal having a frequency within a predetermined set of frequencies, the method further includes providing a two-way digital signal in a second polarization and a second direction to the first area, the two-way digital signal having a frequency within the predetermined set of frequencies, wherein the second polarization is orthogonal to the first polarization.
The present invention also includes a system for distributing information in a MMDS network comprising a digital video signal transmitter, wherein the video signal has a first polarization. In addition, the video signal has a frequency within a predetermined set of frequencies. The system also includes a digital video signal receiver at a receiver site and a digital communication signal transmitter for transmitting communication signals wherein the communication signal has a second polarization. The communication signal has a frequency within the same predetermined set of frequencies. Finally, a digital communication signal receiver is located at the receiver site in a direction that differs from the digital video signal receiver.
The present invention allows the network operators to provide greater than 295 channels (3 Mb/s each) of digital broadcast video simultaneously with a complete two-way service using the same spectrum in the same protected service area as those used for the digital broadcast video. The two-way service can include telephony, video conferencing, and internet access.
The cross-polarization technique and the overlay network design will be more fully understood by reference to the following drawings.